The World Wide Web (“WWW”) is comprised of millions of documents (web pages) formatted in Hypertext Markup Language (“HTML”), which can be accessed from thousands of users through the Internet. To access a web page, its Uniform Resource Locator (“URL”) must be known. Search engines index web pages and make those URLs available to users of the WWW. To generate an index, a search engine, such as Compaq Computer Corporation's ALTA VISTA search engine, may search the WWW for new web pages using a web crawler. The search engine selects relevant information from a web page after analyzing the content of the web page and saves the relevant information and the web page's URL in the index.
Web pages also contain links to other documents on the WWW, for example, text documents and image files. By searching web pages for links to image files, a search engine connected to the WWW, such as Compaq Computer Corporation's ALTA VISTA Photo Finder, provides an index of image files located on the WWW. The index contains a URL and a representative image from the image file.
Web pages also contain links to multimedia files, such as video and audio files. By searching web pages for links to multimedia files, a multimedia search engine connected to the WWW, such as Scour Inc.'s SCOUR.NET, provides an index of multimedia files located on the WWW. SCOUR.NET's index for video files provides text describing the contents of the video file and the URL for the multimedia file. Another multimedia search engine, WebSEEK, summarizes a video file by generating a highly compressed version of the video file. The video file is summarized by selecting a series of frames from shots in the video file and repackaging the frames as an animated GIF file. WebSEEK also generates a color histogram from each shot in the video to automatically classify the video file and allow content-based visual queries. It is described in John R. Smith et al. “An Image and Video Search Engine for the World-Wide Web”, Symposium on Electronic Imaging: Science and Technology—Storage and Retrieval for Image and Video Databases V, San Jose, Calif., February 1997, IS&T/SPIE.
Analyzing the contents of digital video files linked to web pages is difficult because of the low quality and low resolution of the highly compressed digital video files.